I had this issue as well... wanted to use it to power a mob crusher which uses 40 RF/tick and I wasn't getting enough power, so I switched to wind turbines.
Ironically, after I left my Thermoelectric Boiler and returned to it, it went up from where it was before (from about 19 mb/t to 38-39/mb/t per fuelwood heater). Also, I found out the best way to deliver water to it was a reinforced servo on a fluiduct from Thermal. Keeps up and passes the rate of the boil, allowing it to stay full of water. I know they can get hot and not explode, but I prefer not to let all that heat go to waste. Thank goodness for Bonzai Trees or I'd never keep up with the wood demand either!